1. Field of the Invention
This invention pertains to a process for improving the dyeability of carpet yarns made from copolymers of nylon 66 and small amounts of nylon 6.
2. Description of the Prior Art
Polyamide yarns, particularly nylon 66, are highly preferred for use in carpets because of their durability and crimp/bulk retention under hard wear conditions. Although nylon 66 is easier to dye than many other fibers, large amounts of heat energy are used in the dyeing operation. For example, in the batch dyeing of nylon 66 carpet by the method called Beck dyeing, the carpet has had to be maintained in an agitated dye liquor at temperatures near boiling for 30-45 minutes to insure adequate, uniform penetration of dye into the fiber structure. While Beck dyeing without the application of heat has been suggested, it has not been possible to achieve uniform dye uptake throughout the carpet piece in a time period that would be practical for a commercial carpet dyeing operation. Continuous dyeing equipment is a more recent innovation in carpet dyeing. In this type of an operation, the carpet moves continuously as dyes are applied by such means as immersion in a dye bath, spraying or printing. The dyes are then fixed by passing the carpet through a steam chamber at a rate that will provide sufficient retention time to allow the dye molecules to penetrate within the polymer and attach to the polymer chains. Thus, in both Beck dyeing and continuous dyeing, large amounts of energy must be expended to achieve uniform durable colors in carpet yarns.